DOC PREVIEW
USC BISC 307L - Evolutionary Perspectives
Type Lecture Note
Pages 5

This preview shows page 1-2 out of 5 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 5 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 5 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 5 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

What is evolution?Descent with modificationOutcome is an organism matched to its environmentMatching during evolution optimizes reproductive successMatching optimizes REPRODUCTIVE successCalled FITNESS- the probability that one's genes will be passed on to the next generationResults within a population optimizes the average fitness within a particular environmentWill not optimize life spanEvolution does not optimize lifespan or general healthNatural selection is driving forceMechanisms of evolution- Darwin’s observations1. Species produce more offspring than the environment can support2. There is always variation within a population with the ability to compete for resources, survive, and reproduce3. Some variation is inheritedDue to 3 sources1. Mutations2. Recombinations3. Epigenetic modifications(4). Developmental Plasticityenvironment affects phenotype during development and also nervous systemBecause of these observations..4. Differences that produce offspring in more successful forms will be more prevalent- natural selection5. Selection will lead to change in the population evolution (micro or macro)Natural Selection is NOT equal to survival of the fittestSelection maximizes reproductive fitness, not health or longevityCant apply these principles to social aspects of lifeONLY REPRODUCTIVE FITNESSSurvival of genes not survival of health or well beingEvolutionary success of humans does not require long lifeBefore, people did not live long enough to contract the diseases we contract nowHistorical life span of humans makes sense if we look at human fertility with agePuberty is happening earlier and earlierReproductive health peaks in 20’sReproductive disease affects people in their 20s- Natural selection therefore optimizes things that occur during reproductive life onlyHeart Failure- if our body is such a great system why is it designed to blow up?Because disease of middle and advanced lifeThese mechanisms work well in young reproductive peopleExamples of Evolutionary “Flaws”Humans are bipedal and have large brainsEvolution results in compromisesBipedalism requires narrow pelvis vs. newborn survival requiring large headNarrow pelvis is not good for reproductionBig brain means babies head is bigBabies are altricial- meaning they need extended parental careWe are unusual because we stand up and have large brainsWhy is this important?None of our ancestors are bipedalOur spine has a curve and is weakWe are topheavy- too much weight on legsWe need assistance for birthHuman babies must rotate in womb and be in right position to fit through birth canalSuccess rate of human birth is 85% without assistanceSo why are we like this?Early moms probably did not get help with giving birth but we find ways to get around thisEvolution is about compromisehuman pelvis is as wide as it can be to allow for walking and running and for a baby's headLarge brain sizehead cannot be fully developed at birthbrains born immature (don’t mature until 30yrs old)As a result women don’t have very many babieswe are inhibited to have too many babiesHuman body is full of “Design” Flaws1. Why the appendix?Has no known function but was probably used as a pouch to help digest foodWe cannot modify- cant start over2. Can’t synthesize vitamin CProbably because our ancestors ate a lot of fruit3. Inside-out retinalight has to pass through everything else to get to the light sensitive cells and then the light is distortedmakes sense in evolutionary terms because nerves and blood vessels supply from the outside4. Crossing of trachea and esophaguswe can choke and get lung infections pretty easilyprobably evolved from lung fishWhy Do We Get Sick?Proximate Reasons (Pathophysiology) examples:Hypertension is due to an increase in vascular resistanceSickle cell anemia is due to mutation in hemoglobin geneCerebral palsy is due to asphyxia during birthCystic fibrosis is due to mutation in chloride channel geneUltimate Reasons (Evolutionary Medicine approach)Four reasons for why we are vulnerable:1. Fitness is not about health and wellbeing2. Constraints and tradeoffs are inevitable3. Human evolution is too slow to cope with challenges of changing environmentFirst change in environment was slow so evolution worked but then the environment started changing fasterThe last 10000 years have shown a lot happening topographicallyCan lead to mismatching between human adaptations and challenges of the environmentEx: lactose intoleranceHuman evolution much slower than pathogen evolution- drug resistance4. Our evolved defenses may be harmful or seem harmfulEvolution has given us powerful immune defenses but excessive reactions cause harmFever can cause seizures, brain damageAllergies, asthma, anaphylaxisAutoimmune diseaseWhy weren’t these diseases eliminated?The immune system is complicatedThe environment during early life can shape the development of the immune system (developmental plasticity)Clues:1. In developing countries early malnutrition results in more susceptibility to disease later in life2. In Sweden the infectious diseases have dropped due to improved health care and hygiene.Hygiene HypothesisExplains why chronic disease is increasingFound that incidence of chronic disease higher in those who are raised in hygienic cities as opposed to farmsThis suggests that in order for the immune system to develop its regulatory mechanisms it needs to undergo certain exposures during developmentWithout being challenged by normal pathogens the immune system doesn’t develop its full regulatory pathBISC 307L 1st Edition Lecture 1 Current LectureWhat is evolution?- Descent with modification- Outcome is an organism matched to its environmento Matching during evolution optimizes reproductive success- Matching optimizes REPRODUCTIVE successo Called FITNESS- the probability that one's genes will be passed on to the next generation o Results within a population optimizes the average fitness within a particular environment o Will not optimize life span- Evolution does not optimize lifespan or general health- Natural selection is driving force Mechanisms of evolution- Darwin’s observations- 1. Species produce more offspring than the environment can support- 2. There is always variation within a population with the ability to compete for resources, survive, and reproduce - 3. Some variation is inheritedo Due to 3 sources 1. Mutations 2. Recombinations 3. Epigenetic modifications (4).


View Full Document

USC BISC 307L - Evolutionary Perspectives

Documents in this Course
Load more
Download Evolutionary Perspectives
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view Evolutionary Perspectives and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view Evolutionary Perspectives 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?